Electrical apparatus



D. C. LOUDON ELECTRICAL APPARATUS Original Filed Jan. 12, 1962 June 1,1965 l" INVENTOR.

DONALD C. LOUDON BY gf flww ATTOR EYS United States Patent 3,186,397ELECTRICAL APPARATUS Ronald C. London, Sidney, N.Y., assignor to TheBendix Corporation, Sidney, N.Y., a corporation of Delaware Continuationof appiication Ser. No. 165,908, Jan. 12, 1962. This application June19, 1964, Ser. No. 386,474 22 Claims. (Cl. 123-148) This application isa continuation of application Serial No. 165,908, filed January 12,1962, for Electrical Apparatus, now abandoned.

This invention relates to electrical apparatus, and more particularlyrelates to a system for generating timed electrical pulses. Theapparatus of the invention may be employed to advantage, for example, inan ignition system for an internal combustion engine.

The invention has among its objects the provision of a novel electricalpulse generating system.

A further object of the invention resides in the provision of a pulsegenerating system which does not require the use of a mechanicallyoperated breaker or contacts.

Another object of the invention lies in the provision of a breakerlesspulse generating system which is particularly well adapted for use inignition systems for internal combustion engines.

Yet another object of the invention lies in the provision, in a specificpreferred embodiment of pulse generating apparatus in accordance withthe invention, of novel means for selectively retarding the timing ofgenerated pulses, as for retarding the spark ignition of an internalcombustion engine.

Still another object of the invention lies in the provision, in aspecific preferred embodiment of pulse generating apparatus inaccordance with the invention employing a triggered solid stateswitching device, of novel circuit means for erasing the trigger signalfrom the switching device between pulses.

A still further object of the invention lies in the provision of a pulsegenerating system which is particularly characterized by its simplicity,its economy of manufacture and maintenance, and its long life.

The above and further objects and novel features of the invention willmore fully appear from the following description when the same is readin connection with the accompanying drawing. It is to be expresslyunderstood, however, that the drawing is for the purpose of illustrationonly, and is not intended as a definition of the limits of theinvention.

The sole figure of the drawing is a schematic Wiring diagram of anillustrative preferred embodiment of the pulse generating apparatus inaccordance with the invention, such apparatus being shown employed forproviding ignition spark discharges for an internal combustion engine.

As above indicated, the apparatus of the present invention isparticularly advantageous when employed to supply ignition sparkdischarges for an internal combustion engine. It is to be understood,however, that the apparatus of the invention is capable of a number ofdifferent applications wherein timed electrical pulses or discharges arerequired. The apparatus is particularly characterized by the fact thatit requires no mechanically operated breaker or contacts and thus isfree from the maintenance problems which the use of such breakersentails. In the illustrative embodiment, the apparatus employs a magnetoas its primary source of power, the apparatus including pulse triggeringmeans in the form of a rotating triggering wheel and a picieup coil. Theswitching functions in the system are performed by solid state switchingdevices which have no moving parts. As a consequence, the apparatus ofthe invention will operate for long periods without the necessity ofattention.

Turning now to the drawing, the illustrative system includes a powersupplying and triggering portion, generally designated 10, and an energystorage unit, generally designated 11. Power stored in circuit portion11 is discharged into a circuit including a distributor 12 from whichthe discharge is led to one or more output circuits 14, 14'.

The portion of the system includes a magneto schematically shown at 15,the magneto having a rotor 16 carrying a plurality of angularly spacedmagnetic pole pieces 17. Rotor 16 is shown associated with a magnetofield coil 19 which has a center tap 23 connected to ground, as shown.The opposite ends of coil 19 are connected to an output wire 22 byrectifying diodes 20 and 21, respectively. Thus the magneto functions todeliver direct current to the main supply wire 24 to which wire 22 isconnected.

Wire 24 may be selectively connected to ground 27 by an ignition switchprovided with a movable contactor 26. When switch 25 is operated todisconnect wire 24 from ground, the magneto 15 becomes operative. Tosupplement the output of the magneto at low or cranking speeds, there isprovided a starting vibrator assembly .29 which may be selectivelyoperated to deliver a substantial amount of direct current energy towire 24.

A battery 31 is provided, the negative terminal of the battery beingconnected to ground by wire 32. The positive terminal of battery 31 isconnected by a wire 34 to a starter solenoid 36 through a starter switch37. Solenoid 36 is connected to ground at 39. When switch 37 is closed,solenoid 36 functions to connect wire 40 connected between vibrator 29and the solenoid to the positive terminal of battery 31. Thereupon thevibrator assembly delivers its direct current output through wire 30into wire 24. i

Wire 24 extends intoenergy storage unit 11 where it is connected to afirst, condenser charging circuit and to a second, condenser dischargingcircuit. A storage condenser 41 of substantial capacity, for example,2.00 mid, has one terminal thereof connected to wire 24 through a wire42. The other terminal of condenser 41 is connected by a wire 44 to thecenter terminal 45 of the distributor 12. Such distributor has arotatable central distributing arm 46 which is driven in synchronismwith the engine. Arm 46 sequentia1ly cooperates with a plurality ofspaced electrically conducting segments 47, each of the segments beingconnected to its respective output circuit 14, 14.

Output circuit 14 includes a wire 49 leading from its respective segment47 and connected to one end of the primary winding 50 of a voltagestep-up transformer 51. Transformer 51 has a secondary winding 52connected at one end to the other terminal of primary 50 and to ground.The second end of secondary 52 is connected by a wire 54 to the firstelectrode 55 of an ignitcr gap such as a spark plug. The secondelectrode 56 of the igniter gap is connected to ground by a wire 57.

it will thus be seen that when the center arm 46 makes contact with agiven segment 47 the charging circuit for condenser 41 is establishedfrom wire 24 through the condenser to wire 44 through the distributorthrough the primary winding of the respective step-up transformer and toground. The characteristics of the magneto, of the starting vibratorassembly 29, if it is used, and of the charging circuit are such thatcondenser 41 becomes fully charged soon after the central arm of thedistributor enters into contact with each segment 47 of the distributor.

Connected in shunt across storage condenser 41 is a condenesrdischarging circuit. Such latter circuit includes the wire 24 beyondwire 42, and a solid state switching device 5& interposed between wire24 and ground at 48, the switching device operating to discharge thecondenser after it has been fully charged. Device 59 may be a siliconcontrolled rectifier having an anode 60 connected Patented June 1, 1965amass? Q to wire 24, a cathode 61 connected to a portion of thedischarge circuit leading to ground, and a triggering means or gate 62by means of which device $9 is selectively made conductive. Cathode 61is connected by wires 64 and 65, a breakdown or Zener diode 66 and awire 67 to the further wire 69 which is connected to ground 48. Diode66, which has a low breakdown voltage, is a part of a triggering signalerasing circuit to be described. The discharge of condenser 41 iscompleted through ground, primary 56 of step-up transformer 41, wire 49,segment 47, distributor rotor 4-6, and wire 44. The rush of currentthrough primary 58 upon discharge of condenser 41 induces a high voltagein secondary 52 of the transformer, thereby producing a spark dischargebetween electrodes 55 and 56.

Switching device a is triggered by a triggering mechanism generallydesignated 70 so as to produce a succession of timed spark discharges atthe spark gap. Device 74 includes a pickup coil 71 having a core 72. inthe form of a permanent magnet. Rotating close to coil 7?. is atriggering wheel 74 having a plurality of angularly spaced vanes '75 onits periphery. Wheel 74 is driven in synchronism with rotor 16 of themagneto as by a driving means schematically shown at 7d. Means 76 in theillustrative embodiment includes a speed increasing gear deviceindicated at 77 so that the wheel 74 rotates at a speed faster thanrotor 16. The speeds and angular relationships of triggering wheel 74and of distributor arm 46 are maintained constant by the drivingmechanism 76 and by a driving mechanism 73 by means of which distributorrotor 45 is driven. The parts of the pickup device are so related that avane 75 passes through the magnetic field of core 72 at each time that aspark discharge is required for the engine, the distributor arm 46 thenbeing in contact with the corresponding segment 47.

At each passage of a vane 75 past the pickup coil 71, a triggeringvoltage pulse is produced in the coil. One end of coil 71 is connectedby a wire 79 which extends to one or" the contacts of a normally closedpair of contacts 8t as shown. The other of such contacts is connected toground at 34. The other end of coil 71 is connected by a wire 87 to afurther wire 89 extending to the triggering means or gate 62 ofswitching device 5%. Wire 87 extends to wire 67, there being interposedin wire 87 beyond wire 89 a Zener or breakdown diode 8t}. Zener diode 90may have a rating, for example, of 5.0 volts. Connected in shunt withdiode 99 is a resistor E91 which may have, for example, a resistancevalue of 1.8K ohms.

It will be seen that at each cycle of the spark discharge system thestorage condenser 41 becomes charged and then, while distributor arm 4-6is in contact with the same segment 47, a triggering pulse generated bytriggering means 7% causes switching means 59 to discharge. Switchingmeans 5? may be a device of the type known either as a siliconcontrolled rectifier or a silicon controlled switch. In the illustrativeembodiment, device is a silicon controlled switch of such character thatthe anode voltage must swing negative for a period in excess of 5.0p.550. for the switching device to regain control and to turn The anodevoltage in the disclosed circuit swings negative for a period in excessof such required time, and so such condition is met. There is, however,a tendency for the triggering pulse developed by the pickup 7d at higherspeeds to keep the switch turned on. There is thus employed in theillustrative circuit a trigger eraser circuit which makes the turningoil of the switching device 59 independent of the triggering pulseduration.

The components of such erasing circuit are the abovedescribed Zenerdiode 6d, a resistor connected in shunt with such diode and a condenser92 also connected in shunt with the diode. Resistor 94 may have, forexample, a resistance of SR ohms; condenser 92; may have, for example, acapacity of 0.22 mfd. During the dis charge of storage condenser 41, apositive voltage is placed on condenser 92, the magnitude of suchpositive voltage being governed by the breakdown voltage of diode 66.The magnitude of this voltage is in excess of the positive triggervoltage and therefore removes the effect of the triggering pulse on thecontrol switch 59, thereby allowing it to turn oil. The resistor 94bleeds oil the charge on condenser 92 so that the next triggering pulsewill again trigger the switching device 59.

The illustrative ignition system includes means whereby the spark may beselectively advanced, if desired. Such spark advancing means includes asmall condenser 85, having a capacity on the order of .01 mid, which isconnected at one terminal to wire 79 and at the other terminal to groundat $5. When wire 79 is connected directly to ground 84 by the closedcontacts St}, the spark discharges will occur at a first predeterminedtime in the engine cycle. When, however, contacts 86 are opened and wire7? is connected to ground only through condenser the spark dischargetakes place at a predeterminer earlier time in each engine cycle.

Contacts 8%, which are part of a relay generally designated 82, may beselectively opened by energizing the coil 31 of such relay. The relaycoil may be energized by the battery 31, the positive terminal of thebattery being connected by a wire 95 through a switch 97 having amovable contactor 96. The fixed contact of switch 97 is connected torelay coil 81 by wire $9, as shown.

The system shown includes a Zener diode 1% which is interposed in wireTill extending between wire 24 and ground at 1132. Diode ltlll may, forexample, have a breakdown voltage of 200 volts and a rating of 50 watts.Such diode, which is connected in shunt with the switching device 59,protects such device in the event that the primary winding 5% oftransformer 51 should develop an open circuit.

The ignition system shown is suitable, for example, for use with an 8cylinder, 4 cycle engine, the magneto and distributor rotors beingconnected to the engine to run at one-half crank shaft speed. The systemshown, however, when suitably modified, may be employed with a greatvariety of internal combustion engines of different types and numbers ofcylinders. The system of the invention is particularly advantageousbecause Of its freedom from mechanically operated breaker contacts. Thesystem thus requires very little maintenance over long periods of use.The circuit of the invention is also stable under wide variations oftemperature, producing sati factory results, for example, over atemperature range of 30 F. and below to at least 200 F.

Although only one embodiment of the invention has been illustrated inthe accompanying drawing and described in the foregoing specification,it is to be expressl understood that various changes, such as in therelative dimensions of the parts, materials used, and the like, as Wellas the suggested manner of use of the apparatus of the invention, may bemade therein without departing from the spirit and scope of theinvention as will now be apparent to those skilled in the art.

What is claimed is:

1. Apparatus for generating electrical pulses and distributing thepulses in succession to a plurality of output devices connectable to acommon conductor, comprising a storage condenser, a charging circuitincluding a current source for the condenser, said charging circuitcomprising a distributor eriodically connecting one terminal of thecurrent source to the common conductor through each of the outputdevices in succession, circuit means for periodically discharging thecondenser through each of the output devices in succession, saiddischarging circuit means including said distributor and a switchingdevice selectively rendered electrically conductive and non-conductive,and timed triggering means for con trolling the switching device.

2. Apparatus as claimed in claim 1, wherein the distributor includesmeans successively connected in both the charging circuit and thedischarging circuit means whereby during any given charging anddischarging cycle of the condenser the same output device forms a partof the charging circuit and the discharging circuit means.

3. Apparatus as claimed in claim 1, wherein each of the output devicescomprises a transformer having a primary winding and a secondarywinding, and a discharge gap connected to be energized by the secondarywinding of the transformer, the primary winding being connected in thecharging circuit and in the discharging circuit means by thedistributor.

4. Apparatus as defined in claim 1 wherein the switching device isnormally non-conductive electronic switching device.

5. Apparatus for generating a succession of timed electrical pulses,comprising a storage condenser, a charging circuit for the condenser, acircuit for periodically discharging the condenser, said circuits havinga coil winding in common, an output circuit connected to be energized bythe discharge of the storage condenser through said winding, the outputcircuit including at least one discharge gap, said discharging circuitincluding a solid state electronic switching device selectively renderedelectrically conductive and no-conductive, and triggering means forcontrolling the switching device.

6. Apparatus as claimed in claim 5, wherein the triggering meansincludes means for generating a succession of timed electricaltriggering pulses and for delivering such timed pulses to the switchingdevice.

7. Apparatus as claimed in claim 6, wherein the triggering meansincludes a pickup coil and atriggering wheel rotating past the pickupcoil to generate said triggering pulses in the coil, and comprising acapacitor and means selectively to operatively connect the capacitor inseries with the pickup coil to thereby vary the timing of thedischarging of the storage condenser.

8. Apparatus for generating a succession of electrical pulses comprisinga storage condenser, a charging circuit for the condenser, a circuit fordischarging the condenser,

said discharging circuit including a solid state switching deviceselectively rendered electrically conductive and nonconductive, saidswitching device being a rectifier having an anode, a cathode and atriggering gate, said rectifier being rendered conductive upon thereception at the gate of a positive triggering pulse having a minimumthreshold value,

charge on the gate following each discharge of the storage condenserthrough the rectifier, and triggering means for generating a successionof electrical triggering pulses for controlling the switching device.

9. Apparatus as claimedin claim 8, wherein the circuit means for erasingthe residual positive charge on the gate comprises a breakdown diode,resistor and a condenser connected in parallel, said parallel connectedbreakdown diode, resistor and condenser being connected in series in thedischarging circuit.

10. An ignition system for an internal combustion engine having aplurality of cylinders, comprising a storage cc ndenser, an outputdevice for each engine cylinder comprising a transformer and an ignitergap, charging circuit means including a current source for charging saidcondenser through the primary winding of a said transformer, dischargingcircuit means including a normally non-conductive electronic switchingdevice for discharging said condenser through the primary winding of asaid transformer, a distributor for periodically successively connectingthe transformer primary windings in series with said condenser in saidcharging circuit means and said discharging circuit means, and means forcontrolling the switching device to periodically render the samesuccessively conductive and non-conductive to the charge on thecondenser.

11. Apparatus as claimed in claim 10, wherein the distributor includesmeans for simultaneously connecting the circuit means for erasing theresidual positive vice to render the same said primary winding in boththe charging circuit and the discharging circuit of the storagecondenser during each charging and discharging cycle thereof.

12. An ignition system as claimed in claim 10, wherein the means forcontrolling the conductivity of the switching device includes a pickupcoil and a triggering wheel rotating past the pickup coil to generatetriggering pulses in the coil, and a capacitor adapted to be operativelyconnected in series with said pickup coil to vary the timing of thedischarge at the igniter gap.

13. An ignition system as defined in claim 10 wherein the means forcontrolling the conductivity of the switching device comprises abreakdown voltage diode series connected in the anode-cathode circuit ofthe switching device and a capacitor connected in shunt across saiddiode.

14. An ignition system as defined in claim 13 comprising a resistorconnected in shunt across said capacitor for dissipating the residualcharge thereon while the switching device is non-conductive.

15. Electrical pulse generating apparatus comprising a storagecondenser, means for charging said condenser, and a discharge circuitfor said condenser comprising a normally non-conductive electronicswitching device, a breakdown voltage diode connected in series with thecathode of said switching device and a capacitor connected in shuntacross said diode.

16. Electrical pulse generating apparatus as defined in claim 15comprising a resistor connected in shunt across said capacitorfor'dissipating residual charges on said capacitor.

17. Electrical pulse generating apparatus as defined in claim 15comprising means for applying intermittent triggering pulses to thecontrol electrode of said switching delatter conductive to the charge onthe storage condenser, said diode having a breakdown voltage at least asgreat as the voltage of said triggering pulses applied to the controlelectrode.

18. Electrical pulse generating apparatus as defined in claim 15 whereinsaid switching device is a silicon controlled rectifier having an anode,a cathode and a gate electrode.

19. Apparatus for generating a succession of electrical pulsescomprising a storage condenser, a charging circuit for the condenser, adischarge circuit for the condenser including a solid state normallynon-conductive electronic switching device having an anode, a cathodeand a triggering gate, said switching device being rendered conductiveupon the reception at the gate of an electrical triggering pulse havinga minimum threshold value, means for generating a succession ofelectrical triggering pulses and applying the same to the gate forrendering the switching device conductive to charges on the condenser,and means for removing the effect of the triggering pulse on theswitching device following each discharge of the storage condenserthrough the switching device to thereby facilitate recovery of thelatter to a non-conductive state.

20. Apparatus as defined in claim 19 wherein said means for removing theeffect of the triggering pulse comprises a capacitor series connected insaid discharge circuit and means connected in shunt across the capacitorfor limiting the magnitude of the charge assumed by the capacitor duringeach discharge of the storage condenser.

21. Apparatus as defined in claim 20 wherein said means connected inshunt across the capacitor includes a diode.

22. Apparatus as defined in claim 20 comprising a resistor connected inshunt across the capacitor for dissipating the charge on the latterbetween successive discharges of the storage condenser.

No references cited.

RICHARD B. WILKINSON, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,186,397 June 1, 1965 Donald C. Loudon or appears in the above numberedpat- It is hereby certified that err id Letters Patent should read asent requiring correction and that the sa corrected below.

and in the heading to the printed In the grant, line 1 for "Ronald C.London",

specification, line 3, name of inventor, each occurrence, read Donald C.Loudon Signed and sealed this 19th day of October 1965.

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nest:

EDWARD J. BRENNER RNEST W. SWIDER nesting Officer Commissioner ofPatents

1. APPARATUS FOR GENERATING ELECTRICAL PULSES AND DISTRIBUTING THEPULSES IN SUCCESSION TO A PLURALITY OF OUTPUT DEVICES CONNECTABLE TO ACOMMON CONDUCTOR, COMPRISING A STORAGE CONDENSER, A CHARGING CIRCUITINCLUDING A CURRENT SOURCE FOR THE CONDENSER, SAID CHARGING CIRCUITCOMPRISING A DISTRIBUTOR PERIODICALLY CONNECTING ONE TERMINAL OF THECURRENT SOURCE TO THE COMMON CONDUCTOR THROUGH EACH OF THE OUTPUTDEVICES IN SUCCESSION, CIRCUIT MEANS FOR PERIODICALLY DISCHARGING THECONDENSER THROUGH EACH OF THE OUTPUT DEVICES IN SUCCESSION, SAIDDISCHARGING CIRCUIT MEANS INCLUDING SAID DISTRIBUTOR AND A SWITCHINGDEVICE SELECTIVELY RENDERED ELECTRICALLY CONDUCTIVE AND NON-CONDUCTIVE,AND TIMED TRIGGERING MEANS FOR CONTROLLING THE SWITCHING DEVICE.